High speed digital communication receiver

Abstract

An improved high speed digital communications diversity receiver using a forward adaptive transversal filter equalizer, having a plurality of weighting sections in each diversity channel to provide a combined weighting signal, wherein the required complex multiplications and correlations needed for weighting purposes are performed at IF frequencies, while the time-delayed combining operations for providing the desired combined weighted output signal are performed at baseband frequencies. Such an arrangement reduces the number of tapped delay lines normally needed for such transversal filter equalizer operation and further reduces the signal losses incurred in operating delay line devices at intermediate frequencies so that fewer large gain-bandwidth product amplifiers are required in the system than the number required in previously available systems using such forward transversal filter equalizers.

What is claimed is: 
     
       1. A receiver for processing signals transmitted through a dispersive medium from a transmitter and received in a plurality of diversity channels, said receiver comprising forward transversal filter equalizer and combining means responsive to said received signals in each of said channels for processing said received signals to produce a combined demodulated weighted output signal, said forward transversal filter equalizer and combining means including weighting means associate with each said diversity channel and responsive to the received signal at said channel and to an error signal for producing a plurality of weighted signals at each said channel;   means for selectively combining said plurality of weighted signals to produce a plurality of combined weighted signals;   means for demodulating each of said plurality of combined weighted signals to produce a plurality of demodulated weighted signals; and   time delay and combining means responsive to said demodulated weighted signals for combining said demodulated weighted signals at selected time spaced intervals to produce said combined demodulated weighted output signal; and   means responsive to said combined demodulated weighted output signal to produce said error signal.     
     
     
       2. A receiver in accordance with claim 1 and further including means responsive to said derived error signal for producing a plurality of groups of error signals; and   further wherein said weighting means associated with each said channel includes means responsive to the received signal at said channel for providing a first plurality of undelayed received signals and a second plurality of received signals time delayed by a second selected time interval;   a plurality of weight control means responsive to said plurality of time delayed received signals and to a selected group of said plurality of groups of error signals for producing a plurality of weight control signals; and   means responsive to said plurality of undelayed received signals and to said plurality of weight control signals for producing said plurality of weighted signals.     
     
     
       3. A receiver in accordance with claim 2 where said means for producing said plurality of groups of error signals includes means responsive to said derived error signal for providing a first plurality of error signals time delayed by time intervals substantially equal to said first selected time intervals; and means responsive to said first plurality of error signals for providing said plurality of groups of said error signals.   
     
     
       4. A receiver in accordance with claims 1, 2 or 3 and further including amplifying means responsive to each of said plurality of combined weighted signals for supplying amplified combined weighted signals to said demodulating means.   
     
     
       5. A receiver in accordance with claim 4 wherein each said amplifying means comprises a pair of amplifiers. 
     
     
       6. A receiver in accordance with claim 4 wherein the amplifiers of each said amplifying means each have gain-bandwidth products sufficiently large to insure phase stability thereof with temperature. 
     
     
       7. A receiver in accordance with claim 1 wherein the number of diversity channels is D and the number of said combined weighted signals is N, said time delay and combining means effectively corresponding to a single tapped delay line device and the number of said demodulating means being equal to N. 
     
     
       8. A receiver in accordance with claim 6 wherein the number of diversity channels is D and the number of said combined weighted signals is N, the number of said amplifiers being equal to 2N. 
     
     
       9. A receiver in accordance with claim 1 wherein said plurality of weighted signals are combined to produce a plurality of weighted signals at intermediate frequencies; and said demodulating means produces a plurality of weighted signals which are time-delayed and combined by said time delay and combining means to produce said combined demodulated weighted output signal at baseband frequencies.